This study was performed to test the feasibility of early SPECT imaging with 99mTc-tetrofosmin with the presence of high hepatic activity.
Methods: Thirteen normal volunteers were injected 600-740 MBq of 99mTc-tetrofosmin at rest and were imaged at 10 min and 1 hr after injection. The SPECT images were reconstructed for 180 degrees 360 degrees data. The early and delayed SPECT and anterior planar projection images were analyzed.
Results: After excluding one subject because of high hepatic activity overlapping to the myocardium, 4 of 12 subjects (33%) had abnormal scans with reduced uptake in the inferior wall on the early 180 degrees SPECT image. In contrast, only one (8%) showed equivocally reduced uptake on the 360 degrees SPECT image. In the delayed images, all subjects had a normal 180 degrees and 360 degrees SPECT scan. Quantitative data showed reduced regional activities in the inferior wall on the early SPECT scan, especially in the 180 degrees data. There were no changes in the mean anterior-to-inferior ratio in the anterior planar projection images over time, suggesting that the reduced activity in the early SPECT images reflected an artifactual effect.
Conclusion: Our data indicate that it would be best to perform late imaging in patients with suspected coronary artery disease using 99mTc-tetrofosmin.